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Globally, deformation along obliquely converging plate margins produce a wide variety of complex fault patterns, including crustal pop-ups, fault duplex structures, restraining bends, and flower structures. Depending on the plate velocity, plate obliquity, crustal rheology, length-scale, and climate, the evolution of faulting into translational and vertical strain can range in complexity and fault slip partitioning (i.e. vertical vs. horizontal strain). In this dissertation I studied two restraining bends to understand how these factors influence patterns of deformation along two major plate boundaries: The North American-Caribbean and the North AmericanPacific plate boundaries. First, I estimate the exhumation and cooling history along the Blue Mountains restraining bend in Jamaica using multiple thermochronometers. Three phases of cooling have occurred within Jamaica: 1) initial rock crystallization and rapid emplacement of plutons from 75-68 Ma, 2) slow cooling from 68-20 Ma, and 3) two-stage exhumation from 20 Ma – Present. During the most recent phase of Jamaica’s cooling history, two stages of exhumation have been identified at 0.2 mm/yr (20 – 5 Ma) and ~1 mm/yr (5 Ma – Present). Given the plate velocity to exhumation rate ratio during the most recent phase, we suggest that the climate of Jamaica increases the erosivity of the Blue Mountain suite, whereby the Blue Mountains may be in an erosional stead-state. Second, I studied the long-term evolution of a restraining bend at San Gorgonio Pass in southern California by relating fault kinematics within the uplifted San Bernardino Mountains to the nearby Eastern California shear zone. Using highresolution topography (i.e. UAV and lidar surveys), I studied the plausibility of faulting along two potentially nascent faults within the San Bernardino Mountains, namely the Lone Valley and Lake Peak faults. We found that while both faults display evidence for Quaternary faulting, deciphering true fault slip rates was challenging due to the erosive nature of the mountainous landscape. Coupled with evidence of Quaternary faulting along other faults within the San Bernardino Mountains, we suggest a western migration of the Eastern California shear zone.

Abstract: The Maritimes Basin of Atlantic Canada is a structurally and stratigraphically complex basin filled from the Late Devonian to the Permian; it contains smaller subbasins with common stratigraphy separated by fault-controlled basement uplifts. The Sackville and eastern Moncton Subbasins are located in southeastern New Brunswick. Seismic data show localized unconformities within the Horton Group that indicate a complex history of movement. Basement faults controlled sedimentation and deformation during the late Devonian and early Tournaisian. In the Tournaisian and Visean, the region was shortened in association with dextral strike-slip, and normal listric faults were inverted. Low-angle faults intersect to form tectonic wedges that controlled local stratigraphy as they were inserted southward into Visean evaporites and initiated salt expulsion in the subbasins. When the seismic data are artificially flattened, restoring pre-Visean geometry, faults are seen to define a positive flower structure. The flower structure collapsed into the evaporites during the late Serpukhovian, rotating the associated tectonic wedges and producing a “wilted” flower structure with low-angle faults.

Bedrock mapping, structural analysis, and geochronology reveal the distribution of lithologies and timing of metamorphism and deformation in the western half of the Petersham 7.5’ quadrangle, western Massachusetts. Underlying lithologies are: (from west to east) the Ordovician Monson granitic orthogneiss, Silurian Rangeley migmatitic paragneiss, and Late Devonian (357 Ma) Hardwick tonalitic orthogneiss. Their tightly folded contacts strike north to south. The 361 Ma, unfoliated, strike-parallel Nichewaug quartz-diorite (10-100 m wide) intrusion spans the map area within the Rangeley. Evidence for vertical and lateral extrusion/escape of the Monson orthogneiss, as observed in the Palmer MA area, is absent. Instead, petrofabrics (foliations and lineations) indicate E-W shortening and N-S stretching concentrated within the Rangeley Fm. and orthogneiss margins. Asymmetric structures at the Rangeley-Hardwick contact indicate localized sinistral displacement parallel to unit boundaries and tectonic fabrics. U-Th-Pb chemical age dating of Rangeley monazite revealed three precise age populations (1 = 344 Ma; 3 = 377 Ma; 4 = 405 Ma) and one broad population divided into two subpopulations: 2b (~370 Ma) and 2a (~ 360 Ma). The similarity in age between tonalitic/dioritic magmatism and monazite growth in the Rangeley suggests regional metamorphism was driven by magmatic heat input from latest Devonian/earliest Carboniferous plutonism.

Kinematic analysis and field mapping of the Homestake shear zone (HSZ) and Slide Lake shear zone (SLSZ) in central Colorado provide new evidence for strain partitioning in the mid-crust at ~1.4 Ga. The northeast-striking, steeply dipping HSZ comprises a ~10-km-wide set of anastomosing ductile shear zones and pseudotachylyte-bearing faults. Approximately 3-km south of the HSZ, the north-northeast-striking, shallowly dipping mylonites of the SLSZ form three 1-10-m-thick shear zone splays. Both top-up-to-the-northwest and top-down-to-the-southeast shear sense are recorded in the SLSZ and HSZ. Oblique stretching lineations in both shear zones show vertical (top-down-to-the-southeast and top-up-to-the-northwest) and dextral movement occurred during mylonite development. Quartz and feldspar deformation mechanisms and quartz [c] axis lattice preferred orientation (LPO) patterns are consistent with deformation temperatures ranging from ~280-500°C in the HSZ to ~280-600°C in the SLSZ. Mean kinematic vorticity and quartz [c] axis LPOs for parts of each shear zone suggest plane and non-plane strain general shear with contributions of 47-69% pure shear and 31-53% simple shear. Based on micro- and mesoscale kinematics along with mean kinematic vorticity values and deformation temperature estimates, we propose that HSZ and SLSZ formed during strain localization and partitioning within a mid-crustal transpressional shear zone system that involved subvertical shuffling at ~1.4 Ga.

Bedrock geology of the East Brookfield quadrangle (EBQ), based on new 1:24000 scale mapping, consists of an interfolded sequence of Rangeley Fm. and Paxton Fm. metasediments, intruded by Early Mississippian tonalitic to granitic orthogneisses and underlain in the western half by folded orthogneisses of unknown age. Pervasive flattening strains have created planar, generally NNE-SSW striking and consistent moderately west dipping foliations. Generally strike-parallel stretching lineations and boudinage structures, with rarer dip parallel stretching lineations, reflect extrusion of CMZ metasediments and orthogneisses with a flattening component. Mapping in the EBQ demonstrates that a transition between deformational mechanisms of the southern Central Maine Zone is located there. Evidence for previously mapped faults was not observed during mapping. Alternatively, map scale folds terminating in the East Brookfield quadrangle likely accommodated the across-strike shortening and repetition of lithologic units of the CMZ during Acadian orogenesis. Aeromagnetic patterns and outcrop data approximate a map scale, east-verging and west-dipping, shallowly north-plunging isoclinal fold consisting of interlayered mafic and felsic gneisses. Constrictional and flattening strains documented in the deformation features of the East Brookfield quadrangle suggest that it is located on/near the eastern margin of the zone of transpression approximated by the Bronson Hill gneiss domes. Outcrop- to meter-scale folds with hinge axes sub-parallel to parallel with regional lineations suggest constrictional deformation in a transpressional regime. Deformation features associated with map-scale folding, extrusion/extension, and flattening of CMZ lithologies in the East Brookfield quadrangle support a regime of transpressional deformation caused by oblique convergence of Avalonian terrane with Laurentia. U-Pb ages and outcrop structural relationships suggest that regional flattening and folding was syn- to late-orogenic in nature and Carboniferous or younger in age. All previous structural fabrics are transposed by late regional flattening. Lithologies of the East Brookfield quadrangle exemplify the nature of the Acadian granulite-facies high, displaying a peak metamorphic assemblage of Crd + Grt + Sil + Kfs that has undergone retrograde reactions to produce Bt + Sil. Retrograde metamorphism and deformation occurred during strike-parallel extrusion of CMZ lithologies. Retrograde minerals define kinematic/shear sense indicators that record an overall top to the NNE or ENE asymmetry on vertical faces and dextral west side north on horizontal surfaces. Progressive deformation of CMZ lithologies through transpressional mechanisms is proposed as an alternative to the sequential development of Acadian deformational features in three separate stages.

Deformation in southern Alaska is controlled by the accretion and partial subduction of the Yakutat terrane as margin-parallel motion transitions to subduction. Recent studies have shown that deformation in the St. Elias orogen, at the northern end of the terrane, accommodates a large portion of convergence, but deformation at the eastern and southern margins remains more poorly constrained. Rapid recent sedimentation (> 1cm/yr) and glacio-isostatic uplift rates (> 3 cm/yr) in the Fairweather corridor highlight short-term vertical deformation at the eastern margin; however, the relationship between these rates and long-term deformation is less well known. New low-temperature cooling ages are reported along the eastern flank of the St. Elias orogen, placing constraints on vertical deformation over the past few million years. Young cooling ages (< 3 Ma) occur in a broad zone, extending along the onshore length of the strike-slip Fairweather fault. These ages indicate that protracted convergence has been accommodated in the Fairweather corridor. Average (~1 mm/yr) and peak (~3 mm/yr) late Cenozoic exhumation rates are similar to rates to the north, and suggest that the orogen is actually boomerang-shaped in map view. If ~1 mm/yr exhumation has been steady, the onset of rapid exhumation is constrained to post-12 Ma, but likely occurred at 5 Ma with changes in climate and plate obliquity. Although cooling ages reveal no coherent regional pattern relative to known structures, they indicate the margin accommodates a significant component of pure shear and is slip-partitioned. The resolved magnitude of convergence in the Fairweather corridor also indicates that Yakutat terrane motion is rotated from Pacific plate motion, and likely requires significant slip on the Transition fault at the southern edge of the Yakutat terrane. Although million-year exhumation rates are rapid, they are slower than short-term rates related to deglaciation.

Eastward migration of the Caribbean plate relative to the South American plate is recorded by a 1100-km-long foreland basin which is oldest in the west (Maracaibo basin, 65-55 Ma) and youngest in the east (Columbus basin, eastern offshore Trinidad, 15-0 Ma). Regional transpression has caused lithospheric loading and flexure along the northern margin of South America creating a large foreland basin area which propagated from west to east as the Caribbean plate moved eastward relative to the South American plate. I have integrated 775 km of deep-penetration 2D seismic lines acquired by the 2004 BOLIVAR survey, 325 km of 1975 GULFREX seismic data, 8,000 km2 of industry 3-D seismic data, and published industry well data from offshore eastern Trinidad. Interpretation of seismic sections tied to wells reveals the following fault chronology: 1) middle Miocene thrusting along the Darien ridge related to highly oblique convergence between the Caribbean plate and the passive margin of northern South America; continuing thrusting and transpression in an oblique foreland basin setting through the early Pleistocene; 2) early Pliocene-recent low-angle normal faults along the top of the Cretaceous passive margin; these faults were triggered by oversteepening related to formation of the downdip, structurally and bathymetrically deeper, and more seaward Columbus basin; large transfer faults with dominantly strike-slip displacements connect gravity-driven normal faults that cluster near the modern shelf-slope break and trend in the downslope direction; to the south no normal faults are present because the top Cretaceous horizon has not been oversteepened as it is adjacent to the foreland basin; 3) early Pliocene-Recent strike-slip faults parallel to the trend of the Darien ridge and accommodate present-day plate motions. Active mud diapirism in the Columbus basin is widespread and is related to overthrusting and loading of upper Miocene-lower Pliocene age mud. Analysis of the 3-D seismic data reveals the presence of extensive gravity-flow depositional elements on the Columbus basin deepwater area, characterized by mass-transport deposits at the base, turbidite frontal-splay deposits, leveed-channel deposits, and capped by fine-grained condensed-section deposits. Deep basin wells drilled in recent years have proven that turbidites were transported into the Columbus basin deepwater during the Plio-Pleistocene. Analysis of these well results suggest that a deeper oil charge is present within the Columbus basin deepwater area. The primary uncertainty for this variable hydrocarbon system is whether fault or diapiric pathways connect the petroleum charge at depth with shallower reservoir rocks.

Eastward migration of the Caribbean plate relative to the South American plate is recorded by a 1100-km-long foreland basin which is oldest in the west (Maracaibo basin, 65-55 Ma) and youngest in the east (Columbus basin, eastern offshore Trinidad, 15-0 Ma). Regional transpression has caused lithospheric loading and flexure along the northern margin of South America creating a large foreland basin area which propagated from west to east as the Caribbean plate moved eastward relative to the South American plate. I have integrated 775 km of deep-penetration 2D seismic lines acquired by the 2004 BOLIVAR survey, 325 km of 1975 GULFREX seismic data, 8,000 km2 of industry 3-D seismic data, and published industry well data from offshore eastern Trinidad. Interpretation of seismic sections tied to wells reveals the following fault chronology: 1) middle Miocene thrusting along the Darien ridge related to highly oblique convergence between the Caribbean plate and the passive margin of northern South America; continuing thrusting and transpression in an oblique foreland basin setting through the early Pleistocene; 2) early Pliocene-recent low-angle normal faults along the top of the Cretaceous passive margin; these faults were triggered by oversteepening related to formation of the downdip, structurally and bathymetrically deeper, and more seaward Columbus basin; large transfer faults with dominantly strike-slip displacements connect gravity-driven normal faults that cluster near the modern shelf-slope break and trend in the downslope direction; to the south no normal faults are present because the top Cretaceous horizon has not been oversteepened as it is adjacent to the foreland basin; 3) early Pliocene-Recent strike-slip faults parallel to the trend of the Darien ridge and accommodate present-day plate motions. Active mud diapirism in the Columbus basin is widespread and is related to overthrusting and loading of upper Miocene-lower Pliocene age mud. Analysis of the 3-D seismic data reveals the presence of extensive gravity-flow depositional elements on the Columbus basin deepwater area, characterized by mass-transport deposits at the base, turbidite frontal-splay deposits, leveed-channel deposits, and capped by fine-grained condensed-section deposits. Deep basin wells drilled in recent years have proven that turbidites were transported into the Columbus basin deepwater during the Plio-Pleistocene. Analysis of these well results suggest that a deeper oil charge is present within the Columbus basin deepwater area. The primary uncertainty for this variable hydrocarbon system is whether fault or diapiric pathways connect the petroleum charge at depth with shallower reservoir rocks.

The White Mountain shear zone (WMSZ) is a zone of intense penetrative deformation that lies along the western front of the northern White-Inyo Range in eastern-most California and western-most Nevada. The northern half of the WMSZ is characterized by a NNE to NNW-striking steeply dipping foliation and associated shallowly plunging NNE to NW-trending stretching lineations. S-C fabrics observed in outcrop, microstructural shear sense indicators and kilometer-scale foliation geometry all indicate dextral movement. Localized discrete zones of coeval steeply plunging stretching lineations are present in the northern half of the WMSZ. Microstructural data from these domains indicate a high component of pure shear within a separate coeval kinematic framework and hence a transpressional history. The WMSZ appears to be tectonically related to both the Sierra Crest shear system to the west and the Santa Rita shear system to the south. Correlation between the WMSZ and the Santa Rita shear system indicates that Late Cretaceous dextral transpression may extend up to ~120 km along the western front of the White-Inyo Range. Cross-cutting relationships with Late Cretaceous plutons bracket the age of the WMSZ at between 72-92 Ma. A lack of annealing recrystallization in deformed quartz and the presence of high temperature crystallographic fabrics near the margins of the ca. 72 Ma Boundary Peak pluton indicate significant strain accumulation within the WMSZ subsequent to emplacement of the Boundary Peak pluton. These observations extend the duration of Late Cretaceous dextral transpression in eastern California to at least as recent as 72 Ma.

The Gold Hill fault zone is a first-order structure in the Carolina Zone of the southern Appalachians that separates medium grade ductiley deformed rocks of the Charlotte terrane from low grade, mildly deformed rocks of the Carolina terrane. Based on circumstantial evidence, the Gold Hill fault zone has traditionally been viewed as a Devonian dextral shear zone. However, at the western boundary of the Carolina terrane, Late Ordovician, northeast trending, en echelon regional folds are truncated by the north-northeast-trending Gold Hill fault zone. The orientation of these folds relative to the trace of the Gold Hill fault zone suggests previously undocumented early sinistral shear along this major structure. In this vein, new work involving structural mapping and modern kinematic analysis has been undertaken near High Rock Lake, North Carolina in order to investigate the early history of the Gold Hill fault zone. At the western boundary of the Carolina terrane in the vicinity of High Rock Lake, lower to middle greenschist facies rocks of the Albemarle Group are folded about the southwest plunging axis of the Silver Valley syncline and imprinted by a steep northeast-striking axial planar cleavage. In this area, the Gold Hill fault truncates structures associated with the Silver Valley syncline and separates two distinct structural domains. The southwestern domain is characterized by lower to middle greenschist facies unseparated Albemarle Group units deformed by upright, southwest-trending, outcrop-scale folds that contain a steep, north-northeast to northeast striking axial planar cleavage. The folds and cleavage in this domain are similar in geometry and style to the Silver Valley syncline and are interpreted to be genetically related to regional folds in the Carolina terrane. The northwestern domain consists of upper greenschist facies phyllitic volcaniclastic rocks of the western belt. Foliation surfaces in this domain, which strike north-northeast and dip steeply, contain a consistent sub-vertical stretching lineation, as well as a heterogeneously distributed sub-horizontal stretching lineation. Kinematic indicators suggest that motion on the Gold Hill fault zone involved thrusting of the western belt (hanging wall) over the Carolina terrane (foot wall) coupled with a component of sinistral strike-slip motion. These new structural and kinematic relationships suggest Late Ordovician or younger sinistral transpression that may be related to the accretion of the Carolina Zone to Laurentia.

Structural field mapping and analyses of the Poverty Hills reveal a complex deformational geometry consistent with that of a transpressional positive-flower-structure uplift. Kinematic indicators show vertical and horizontal translation facilitated by reverse faulting with a strong oblique strike-slip component. The onset of deformation in the Poverty Hills is estimated at ~1.7 Ma, and the Owens Valley fault is proposed to have stepped westwards in kinematic response to the rapid development of regional transtensional fault patterns. Geometric modeling of uplift points to a constant slip rate of 1.27-1.44 mm/yr since ~1.7 Ma on the northern Owens Valley fault. These kinematic, geometric, and temporal relations are utilized to better constrain slip partitioning and distribution across the major fault systems in the region and to characterize the spatial and temporal evolution of the Owens Valley basin, the Owens Valley fault, and the Eastern California Shear Zone in this region.

The Grenville Province is a remnant of a ca. 1.1 Ga orogen, exposed as a continuous belt in northeastern North America. Rocks showing evidence of Grenville-aged deformation occur all over the world and represent the final amalgamation of the Proterozoic supercontinent Rodinia. By studying the timing and nature of motion along crustal-scale, ductile shear zones, it is possible to place constraints on the tectonic history of this part of the Grenville orogen. This, in turn, provides information on how the lithosphere evolves after a major orogenic event and what kinds of driving mechanisms play a major role in post-orogenic modification and stabilization of the crust. To constrain the temporal evolution of these shear zones, a detailed structural and thermochronologic study was undertaken across the Metasedimentary Belt in the southeastern portion of the Grenville Province in Ontario and New York State. Ages are based on radiogenic isotope analysis, using the decay of potassium to argon in the minerals hornblende, biotite, and potassium feldspar, and uranium to lead decay in the mineral sphene. Primarily because of differences in diffusion, different minerals will close to diffusion of radioactive elements at different temperatures. Assuming a general geothermal gradient, these temperatures can be assigned corresponding depths in the crust, and a measurement of ages across a shear zone gives an estimate on the amount and timing of displacement. Coupled with field structural analysis, it is then possible to determine the type of displacement and tectonic significance of these boundaries. In this portion of the Grenville Province, analyses show a protracted tectonic history after the latest episode of contraction. After an initial transpressive event, most shear zones in this part of the Grenville Province are reactivated as extensional zones. Ca. 300 myr later, by 780 Ma, extension has ceased and the region uplifted as a coherent block. Using these time constraints, it is possible to develop quantitative models to explore the physical evolution of the crust. Numerical analyses give some constraints on the behavior of the lithosphere after orogenesis and may give insights on the driving mechanisms that govern post-orogenic extension in mountain belts.

This study documents the deformation history of the Santa Rita Flat pluton, eastern California, from the time of emplacement to post-emplacement transpressional shearing, and consists of manuscripts that make up three chapters. The first chapter addresses the emplacement of the Santa Rita Flat pluton using anisotropy of magnetic susceptibility (AMS). The second chapter describes the kinematic analysis of cross-cutting shear zones within the western margin of the pluton. The third chapter is an informal paper on the U/Pb dating of two sheared felsic dikes from the pluton. AMS of the Santa Rita Flat pluton indicates that the paramagnetic and ferromagnetic minerals define a foliation which is arched into an antiformal structure in the central to southern parts of the pluton. The northern part of the pluton displays an east-west striking magnetic foliation which lacks a fold-like geometry. Previously published field mapping and petrologic surveys of the pluton and surrounding wall rocks indicate that the southern margin and northern part of the Santa Rita Flat pluton represents the roof and core of the pluton, respectively. Integration of our analysis of the internal structure of the pluton with previously published work on the regional structure of the surrounding metasedimentary wall rocks, suggests that the pluton may have initially been intruded as a sill-like or "saddle reef" structure along a stratigraphically controlled mechanical discontinuity in the hinge zone of an enveloping regional-scale synform. Subsequent vertical inflation of this sill resulted in local upward doming of the overlying pluton roof and formation of the antiformal structure now observed at the current erosion level in the central-southern part of the pluton and overlying locally preserved roof rocks. No corresponding fold structure is indicated by AMS analysis in the northern part of the pluton, which is exposed at a deeper level, and represents a section closer to the pluton core. Emplacement of the Santa Rita Flat pluton at 164 Ma overlaps in time with regional deformation at ~185 - ~148 Ma (Middle - Late Jurassic) recognized in the southern Inyo Mountains. Northwest trending folds are pervasive along the western flank of the Inyo and White Mountains, and may have accommodated strains at the lateral tips of thrust faults which crop out in the southern Inyo Mountains. We speculate that space for initial emplacement of the Santa Rita Flat pluton may have been produced by layer-parallel slip and hinge-zone dilation, accompanied by axis-parallel slip during formation of a regional scale thrust-related synform. The Santa Rita shear system (SRSS) is composed of a series of discrete NW-SE striking steeply dipping shear zones that cut and plastically deform granitic rocks of the Santa Rita Flat pluton. The shear zones exhibit a domainal distribution of gently and steeply plunging stretching lineations, and are located at planar mechanical discontinuities between the granite and a series of felsic/mafic dikes which intrude the pluton. Mylonitized dikes within the shear zones contain syntectonic mineral assemblages not observed in dikes outside the shear zones, indicating that the dikes were intruded prior to shear zone development. Correlation with geometrically similar shear zones in the Sierra Nevada batholith to the west, suggests that the SRSS probably nucleated from a regional stress field in Cretaceous times (~90-78 Ma). Strain is heterogeneous within the shear zones, with local development of protomylonite, mylonite, ultramylonite and phyllonite. Strain heterogeneity within the granite is attributed to fluid infiltration and chemical reaction and alteration of feldspar to fine-grained mica. These deformation-induced mineral changes would have resulted in progressive mechanical weakening over time of rocks within the SRSS. The phyllonites occur predominantly within steeply lineated shear zones and contain mylonitized foliation-parallel quartz veins. The pattern of c-axis preferred orientation in these quartz veins indicates that deformation within the shear zones occurred under plane strain conditions. Locally, quartz veins also cut the foliation planes, reflecting high pore fluid pressures during evolution of the SRSS. These cross-cutting quartz veins are also plastically deformed, and their c-axis patterns indicate weak constrictional strains. The orientation of the shear zones, together with their strain paths, are used to develop a transpressional kinematic model for development of the SRSS within a progressively rotating stress field.